This patch fixes inconsistencies in bl1_tbbr_image_descs[]
and miscellaneous fixes in Firmware Update code.

Following are the changes:
* As part of the original FWU changes, a `copied_size`
  field was added to `image_info_t`. This was a subtle binary
  compatibility break because it changed the size of the
  `bl31_params_t` struct, which could cause problems if
  somebody used different versions of BL2 or BL31, one with
  the old `image_info_t` and one with the new version.
  This patch put the `copied_size` within the `image_desc_t`.
* EXECUTABLE flag is now stored in `ep_info.h.attr` in place
  of `image_info.h.attr`, associating it to an entrypoint.
* The `image_info.image_base` is only relevant for secure
  images that are copied from non-secure memory into secure
  memory. This patch removes initializing `image_base` for
  non secure images in the bl1_tbbr_image_descs[].
* A new macro `SET_STATIC_PARAM_HEAD` is added for populating
  bl1_tbbr_image_...